CN110088533B

CN110088533B - Burner tip for installation in a burner, comprising an air channel system and a fuel channel system, and method for producing same

Info

Publication number: CN110088533B
Application number: CN201780078736.2A
Authority: CN
Inventors: C.霍克利; C.基纳; A.克罗策; Y.库斯特斯; M.萨尔谢尔
Original assignee: Siemens AG
Current assignee: Siemens Energy Global GmbH and Co KG
Priority date: 2016-12-22
Filing date: 2017-12-19
Publication date: 2021-02-12
Anticipated expiration: 2037-12-19
Also published as: US20190360696A1; DE102016226061A1; CN110088533A; EP3559556B1; CA3047819C; WO2018114918A1; EP3559556A1; CA3047819A1

Abstract

The invention relates to a burner tip (19) suitable for use in a pilot burner, for example in a gas turbine. The invention also relates to a method for manufacturing a burner tip (19) by an additive manufacturing process, such as selective laser melting. According to the invention, a part of the wall (25) of the burner tip (19) is provided with holes in a porous manner or is designed as a space grid, wherein air from the air channels can be transported through the gaps or open holes in the space grid. The air can thus cool the material of the burner tip (19), which achieves a lower thermal load. The wall structure (25) can be formed in a plurality of layers (26, 27, 28) with different porosities or with different lattice structures.

Description

Burner tip for installation in a burner, comprising an air channel system and a fuel channel system, and method for producing same

Technical Field

The invention relates to a burner tip for installation in a burner, wherein the burner tip has an air channel system which is open to the surroundings of the burner tip and a fuel channel system which is open to the surroundings of the burner tip. The burner tip therefore has openings on its surface, which openings form the connection of the air channel system and the fuel channel system to the surroundings of the burner tip. The environment of the burner tip is formed here, for example, by a combustion chamber in which the fuel delivered by the fuel channel system is burned. The combustion chamber may be arranged, for example, in a gas turbine.

The invention also relates to a method for manufacturing a burner tip having the above-described structure.

Background

A burner tip of the type of construction described at the outset is known, for example, from patent document EP 2196733a 1. The burner tip described in said patent document can be used, for example, in a gas turbine, wherein the burner tip forms the downstream end of a burner lance which is arranged in a main channel for combustion air. The burner tip is constructed as double-walled, wherein the outer wall forms a heat shield which is intended to keep the combustion heat generated away from the inner wall. Between the outer wall and the inner wall, a cavity, i.e. an annular chamber, is thus arranged, through which air can flow for cooling purposes. In the embodiment described, the heat shield must be designed to withstand the thermal loads resulting from the combustion taking place in the downstream combustion chamber. Thus, the outer wall of the burner tip is a limiting factor on the useful life of the burner tip.

Disclosure of Invention

The object of the invention is to develop a burner tip of the type mentioned at the beginning in such a way that the service life of the components is improved. The object of the invention is also to provide a method for producing such a burner tip.

This object is achieved according to the invention by the burner tip described at the outset in that the air duct as part of the air duct system extends centrally in the burner tip and this central air duct is surrounded by an open-pored and/or space-grid-designed wall structure, wherein the holes in the wall structure (in the open-pored wall structure) and/or the grid gaps (in the space-grid-designed wall structure) form a connection between the air duct and the surroundings of the burner tip. The connection is thus part of an air channel system leading to the surroundings of the burner tip. This is achieved for the pores in that the wall structure is open-pored, i.e. the pores form channels which facilitate the transport of air in the air channel system. This also applies to the grid gaps which are interconnected in such a way that an outward air path is formed as part of the air channel system.

The advantage resulting from the configuration of the wall structure is that the surface for heat transfer from the environment of the burner tip into the air flowing in the air channel system is increased. This creates convective cooling, whereby the heat introduced is discharged again after being transferred to the air through the wall structure.

A further advantageous cooling effect is achieved in that the wall structure provides a large number of small openings through the holes or grid gaps on the surface of the burner tip, from which the air flows out into the surroundings of the burner tip. Where an air hood is formed, whose temperature is always lower than the combustion temperature in the combustion chamber, although the air has already risen somewhat in the wall structure. The resulting air cap thus advantageously forms a heat insulation layer and reduces the heat input and thus advantageously additionally reduces the heat load on the burner tip.

According to an advantageous embodiment of the wall structure, the wall structure can consist of a plurality of layers with different porosities (in the case of a wall structure having an open porous structure) and/or different lattice structures (in the case of a wall structure having a structure designed as a spatial lattice), wherein the air channel system passes through the layers in succession. In particular, three layers with different porosities and/or different grid structures can be provided. The layered structure advantageously makes it possible to equip the wall structure layer by layer with the desired properties, wherein the thermal conductivity, mechanical stability and flow resistance in the layer formed by the wall structure can be influenced. It is true here that the larger the available total cross section of the holes or grid gaps, the lower the flow resistance. The flow resistance in large holes or grid gaps is also smaller than in small holes or grid gaps. The heat conduction in the wall structure is determined primarily by the ratio of the volume fraction of the material to the volume fraction of the pores. The greater the volume fraction of the material, the greater the heat conduction. The mechanical stability in materials of open porous design is generally less than in space grids, which can be optimized for mechanical loads when choosing their geometry.

Advantageously, the average pore diameter in adjacent layers decreases from layer to layer, viewed in the direction of the intended flow of the air. In other words, the air flows first through the layer with the larger average pore size and the relatively smaller flow resistance, where it absorbs heat and thereupon flows through the layer with the smaller average pore size, where it can absorb more heat due to the smaller flow velocity and the larger surface area. The large number of holes with a small average size also ensures that a closed air hood is reliably formed when the air flows out into the environment of the burner tip, which air hood provides additional thermal protection.

In order to ensure an optimum cooling effect and an efficient formation of the air cap, the pore size of the pores in the layer adjoining (or referred to as the interface) with the surroundings of the burner tip may be between 10 and 250 μm, preferably between 30 and 170 μm. In the layer adjoining the central air channel, the pore size of the pores may be between 1 and 9mm, preferably between 2 and 6mm, and more preferably between 2.5 and 4.5 mm. Instead of a porous layer, a layer consisting of a spatial grid can also be used, wherein the grid gaps can likewise have a size of between 1 and 9mm, preferably between 2 and 6mm and particularly preferably between 2.5 and 4 mm. As a characteristic variable of the grid, it is also possible to use the hole spacing, wherein the hole spacing is determined as the distance of the respective centers of gravity of the cross sections of the grid gaps from one another and can likewise lie within the above-mentioned value ranges.

If three layers are provided in the wall structure, the pore diameter of the layer situated between the layer adjoining the central air channel and the layer adjoining the surroundings of the burner tip, which is also referred to as the middle of the intermediate layer, is between 150 and 1000 μm, preferably between 200 and 800 μm, and particularly preferably between 250 and 750 μm. Multiple intermediate layers may also be provided.

According to a further embodiment of the invention, an air guide structure is provided in the central air duct. The air guide structure is impinged by the air, whereby the air flow can be directed in a suitable manner. For example, it is possible that the air guide structure is provided with an inner channel directed towards the wall structure. In this way, a uniform air flow can advantageously be provided on the side adjoining the air channel, so that all the holes and/or grid gaps opening out to the air channel are provided with air.

It is also advantageous if a plurality of fuel channels, which are part of a fuel channel system, are guided through the wall structure, wherein the fuel channels are connected to fuel openings in the surface of the burner tip. The fuel openings may advantageously be evenly distributed in the circumferential direction of the burner tip, so that the fuel is evenly introduced into the flowing air and distributed therein. The heat load at the burner tip is also more uniform due to the consequent more uniform combustion of the fuel, thereby avoiding asymmetric heat load peaks.

It is also advantageous if the fuel channel is connected to an annular channel surrounding the central air channel, which is likewise part of the fuel channel system. In this way, the fuel can be fed uniformly into all the fuel channels, so that the amount of fuel released at the different fuel openings is also uniform. The advantages are a homogeneous fuel combustion and a homogeneous thermal loading of the burner tip.

The object is also achieved according to the invention by the method described at the outset in that for the production an additive manufacturing process is used, wherein the wall structure designed as open-pored and/or as a space lattice is produced in one piece with the burner tip. The additive manufacturing process is advantageously also suitable in a particular way for the manufacture of fine grid structures, so that the apertures can be optimally adapted to the specifications of the design. In particular, a fine grid structure having the dimensions already mentioned can be produced. Different porosities may also be created in the manufactured structure, so the wall structure may also be composed of multiple layers during the additive manufacturing process. The wall structure is formed in one piece. The wall structure may also advantageously be additively manufactured in one piece with the rest of the burner tip.

The different porosities in the layers may advantageously be created by varying the introduction of energy into the powder bed of a powder bed based additive manufacturing process. Another possibility is to use different powders. The powder can be metered in position-specifically or in succession when producing the powder bed and then melted. By varying the energy introduction, it is possible, for example, to vary between complete melting of the powder particles (selective laser melting) and sintering of the powder particles (selective laser sintering) by sintering (Anschmelzen) of their surfaces, wherein an open, porous channel system is formed between the particles during the sintering process.

Another possibility is to reduce the energy introduction by increasing the line distance of the illumination line. The line distance may be chosen so large that a part of the particles in the powder bed is not melted, whereby holes are formed in the structure in these areas. The transition from the production of such a hole structure to the production of a lattice structure is continuous here, since the lattice structure is also produced in that the material of the powder bed is melted only in the region where the lattice struts are to be produced.

In accordance with the present application, an additive manufacturing process is understood to be a method in which the material from which the component is manufactured is added to the component during formation. Here, the component has already formed its final shape or at least approximates said shape. The build material is preferably in powder form, wherein the material used to make the component is physically solidified by the introduction of energy by the additive manufacturing process.

To enable the component to be manufactured, data (CAD model) describing the component is prepared for the selected additive manufacturing process. The data are converted into component data adapted to the manufacturing method for generating instructions for the manufacturing device, so that suitable process steps for gradually manufacturing the component can be carried out in the manufacturing device. For this purpose, data are prepared in such a way that geometric data for the layers (Slices) of the component that are to be produced separately are provided, which are also referred to as Slices (Slices).

Examples of additive manufacturing may be, for example, Selective Laser Sintering (also known as SLS), Selective Laser Melting (also known as SLM), electron Beam Melting (also known as EBM, electron Beam Melting), Laser powder build-up (also known as Laser Metal Deposition, LMD, Laser Metal Deposition) or Cold Gas spraying (also known as Gas Dynamic Cold spraying, GDCS, Gas Dynamic Cold Spray). These methods are particularly suitable for processing metallic materials in the form of powders from which structural components can be manufactured.

In SLM, SLS and EBM, the components are manufactured in layers in a powder bed. Thus, these methods are also referred to as powder bed based additive manufacturing processes. In the powder bed, powder layers are produced in each case, which are then melted or sintered locally by an energy source (laser or electron beam) in the region in which the component is to be produced. The components are thus produced in layers and can be removed from the powder bed after the production has been completed.

In LMD and GDCS, powder particles are fed directly to the surface where the material coating should be done. In LMD, the powder particles are melted by a laser directly on the surface in the impact point and form a layer of the component to be produced there. In the GDCS, the powder particles are strongly accelerated, so that the powder particles remain attached to the surface of the component while being deformed simultaneously, mainly due to their kinetic energy.

GDCS and SLS have in common the feature that the powder particles do not completely melt in these processes. This also enables the manufacture of porous structures while maintaining the interstices between the particles. In GDCS, the melting takes place at most in the edge regions of the powder particles, which can fuse on their surface due to strong deformations. In SLS, care needs to be taken in selecting the sintering temperature, which is below the melting point of the powder particles. In contrast, in SLM, EBM and LMD, the amount of energy introduced is intentionally so high that the powder particles are completely melted.

Drawings

Further details of the invention are described below with reference to the figures. Identical or corresponding drawing elements are illustrated only a few times in the differences between the individual figures. In the drawings:

fig. 1 shows a schematic structure of a burner in cross section, in which an embodiment of a burner tip according to the invention is constructed;

FIG. 2 shows an embodiment of a burner according to the invention in cross-section;

fig. 3 shows as a detail view an exemplary embodiment of a method according to the invention, in which a burner according to fig. 2 is produced;

FIG. 4 shows a further embodiment of a burner tip according to the invention in cross section and

fig. 5 shows a detail V according to fig. 4.

Detailed Description

Fig. 1 shows a burner 11, which has a housing 12, in which a main channel 13 for air is formed. The housing is constructed symmetrically about the axis of symmetry 14 and has a burner lance 15 in the center of the main channel 13. The burner lance 15 is fixed in the main channel 13 by a strip 16. Furthermore, guide vanes 17 extend between the burner lance 15 and the housing 12, which guide vanes cause the air to rotate about the axis of symmetry 14, as can be seen from the illustrated air arrows 18.

The burner lance 15 has a burner tip 19 at the downstream end, wherein the burner tip is supplied with air 21 via a central air duct 20 and with fuel 23 via an annular duct 22 arranged around the air duct 20. The fuel 23 may be gaseous or liquid. The air 21 and the fuel 23 are discharged through openings, not shown in detail, in the burner tip and are thus mixed into the air flow from the main channel 13. Here, the air 21 cools the burner tip 19 (which will also be explained in more detail below). The burner 11 operates according to the operating principle of a pilot burner (pilotburner). The burner can be installed, for example, in a combustion chamber, not shown in detail, of a gas turbine, wherein the combustion chamber forms the environment 30 of the burner tip in this case. A fuel gun (not shown) for injecting other fuels may also be arranged in the air channel 21, through which fuel gun air is forced towards the outlet to enter the conical outer surface.

According to fig. 2, a burner tip 19 is shown in section, which can be inserted into the burner 11 according to fig. 1. A central air duct 20 can be seen, which opens into a central outlet opening 24. In the discharge opening an additional fuel gun (not shown) may be arranged as already mentioned. In addition, an annular channel 22 for fuel can be seen.

The burner tip is formed by a wall structure 25 which consists of a layer 26 which adjoins the surroundings of the burner tip 19, an intermediate layer 27 which can also be referred to as a middle layer, and a layer 28 of the air channel 20 which faces the center. Each of the

layers

26, 27, 28 has a different structure, wherein holes 31 (see fig. 3) are provided in the

layers

26 and 27, and grid gaps 32 are provided in the layer 28, which grid gaps are located between grid struts 33 (see fig. 3).

Due to the holes 31 and the grid gaps 32, the wall structure 25 is permeable to air and thus forms part of the air channel system. The air guided through the central air duct 22 partially passes through the outlet opening 24 and partially leaves the burner tip 19 via the wall structure 25. In the central air channel 20, an air guide structure 34 in the form of a guide vane is provided, which facilitates an even distribution of the air over the surface of the wall structure. This is also facilitated by an internal channel 35 in the air guide structure 34, which introduces air into the radially outer edge region of the wall structure 25.

The layer 28 of the air channel 20 facing the center consists of a three-dimensional grid. The grid advantageously has only a low air flow resistance, however, a relatively high mechanical stability is imparted to the wall structure 25. With larger pores in the intermediate layer 27. The holes also form a relatively small flow resistance for the air, but are suitable for finely distributing the air over the entire cross-section of the wall structure, i.e. over the cross-section that is available for the air channel structure. The layer 26 facing the ambient environment 30 has smaller pores than the intermediate layer. This results in a strong increase in the surface in the interior of the layer 26, so that the air flowing through in this region absorbs heat from the surroundings 30 and can be discharged from the burner tip 19 after leaving it. Layer 26 has a smaller thickness than the other layer designs so that the flow resistance created by layer 26 is not excessive.

The annular channel 22 opens peripherally into a plurality of fuel channels 36 which communicate with the surroundings 30 via fuel openings. The fuel is thus introduced into the surroundings 30 uniformly distributed over the outer circumference of the burner tip 19, in order to avoid thermal load peaks at specific locations of the burner tip. Since an odd number of fuel passages 36 are arranged on the outer circumference, a cross-sectional view is formed only on one side of the burner tip 19. The same applies to the air guide structure 34.

Fig. 3 shows how the burner tip 19 according to fig. 2 can be produced in a powder bed 39 by selective laser melting using a laser beam 38. The part of the wall structure 25 can be seen, which consists of a layer 26, which is then directed towards the surroundings 30, an intermediate layer 27 and a layer 28, which is then directed towards the air channel 20. It can be seen that the apertures 31 in layer 26 are finer than the apertures in intermediate layer 27. This can be achieved, for example, by modifying the process parameters of the laser melting. The spatial grid in layer 28 is shown in detail in fig. 3. A cube-shaped grid cell is formed, wherein the hole spacing i is obtained by the distance of the center of gravity S of the cross-section of the grid gap, i.e. the intersection of the diagonals of the relevant square cross-section.

Another embodiment of a combustor tip is shown in fig. 4. The wall structure 25 has an arched shape, wherein the central outlet opening 24 is omitted. The air passes completely through the air channel structure formed by the porous wall structure, wherein the wall structure is again designed as three

layers

26, 27, 28. The fuel channel 36 opens into a fuel opening 37, which is arranged radially on the outside on the burner tip 19.

The construction of the wall structure 25 is shown on a scale in fig. 5 as detail X. In fig. 5, a scale for a length of 1mm is drawn. Each of the three layers is approximately 1mm thick. The layer 26 facing the surroundings 30 and the intermediate layer (middle layer) 27 have holes 31, while the layer 28 facing the air channels 20 is designed as a grid structure with grid bars 33 and grid gaps 32.

The air first passes through the layer 28, wherein the grid structure is designed to facilitate the flow. The air passes through the grid gaps 32 into the coarse pores 31 of the intermediate layer 27, where it is distributed with relatively little pressure loss into the pores 31 of the layer 26. From there, the air enters the surroundings 30 in a manner not shown in detail.

The lattice structure in layer 28 is geometrically designed such that it can be produced by means of a suitable exposure strategy, for example by means of laser melting. Here, the holes 31 in the

layers

26 and 27 can be obtained by a defined exposure strategy. Here, if the gaps between the powder particles do not form sufficient porosity, it is also possible to use an exposure strategy in which the surface of the powder bed 39 is only partially exposed, so that the individual powder particles remain unexposed and can be removed from the component afterwards. The intermediate layer 27 shows the formation of holes which are formed by statistically distributed incomplete exposures of the powder bed, wherein the course of the holes or the exposed areas of the respective powder layers (which correspond to the exposure step and are significantly thinner than the three

layers

26, 27, 28) is random. In the layer 26, the incomplete exposure regime follows a certain pattern, for example a line distance at the time of exposure, the dimensions of which are intentionally chosen such that particles which are not exposed and which have not melted or fused remain between the tracks. Apertures 31 are formed in these areas, wherein the structure of layer 26 resembles a fabric. This is achieved, for example, by twisting the parallel tracks by 90 ° at regular intervals during production. This conversion is performed after a certain number of powder layers, depending on the desired pore size.

Claims

1. A burner tip for installation into a burner (11), wherein the burner tip has an air channel system which is open towards the surroundings of the burner tip and a fuel channel system which is open towards the surroundings of the burner tip,

characterized in that an air channel (20) as part of the air channel system extends centrally at the burner tip and this central air channel is surrounded by a wall structure (25) which is open-pored and/or designed as a spatial grid, wherein the apertures (31) and/or grid gaps (32) in the wall structure (25) form a connection between the air channel (20) and the surroundings of the burner tip as part of the air channel system, the wall structure (25) being composed of a plurality of layers (26, 27, 28) having different porosities and/or different grid structures, wherein the air channel system passes through the layers (26, 27, 28) in succession.

2. A burner tip according to claim 1, characterised in that three layers (26, 27, 28) with different porosity and/or different lattice structure are provided.

3. The burner tip of claim 2 wherein the average pore size in adjacent layers decreases from layer to layer as viewed in the direction of the intended flow of air.

4. A burner tip according to claim 1, characterised in that the pores (31) in the layer (26) adjacent to the surroundings of the burner tip have a pore size of between 10 μm and 250 μm.

5. A burner tip according to claim 1, characterised in that in the layer (28) adjoining the central air channel the aperture of the holes (31) or the grid gaps (32) in the spatial grid have a size of between 1mm and 9 mm.

6. A burner tip according to claim 4, characterised in that in the layer (28) adjoining the central air channel the aperture of the holes (31) or the grid gaps (32) in the spatial grid have a size of between 1mm and 9 mm.

7. A burner tip according to claim 6, characterised in that one or more intermediate layers (27) are present between the layer (28) adjoining the central air passage and the layer (26) adjoining the surroundings of the burner tip, the pores (31) in the intermediate layer or layers having a pore size of between 150 μm and 1000 μm.

8. A burner tip according to claim 1, characterised in that an air guide structure (34) is provided in the central air channel (20).

9. A burner tip according to claim 8, characterised in that the air guide structure (34) is provided with an internal channel (35) directed towards the wall structure (25).

10. A burner tip according to claim 1, characterised in that the central air channel (20) is directed in the burner tip towards a central discharge opening (24).

11. A burner tip according to claim 1, characterised in that said wall structure (25) has a conical or dome-like shape.

12. A burner tip according to claim 1, characterized in that a plurality of fuel channels (36) as part of the fuel channel system are guided through the wall structure (25), and that the fuel channels (36) are open to the surroundings of the burner tip.

13. A burner tip according to claim 12, characterised in that the fuel channel (36) is connected to an annular channel (22) surrounding the central air channel (20), said annular channel being part of a fuel channel system.

14. Method for manufacturing a burner tip according to one of the preceding claims, characterized in that for the manufacturing an additive manufacturing process is used, wherein the wall structures (25) designed as open porosity and/or as space lattice are manufactured in one piece with the burner tip.

15. Method according to claim 14, characterized in that the wall structure (25) is manufactured from a plurality of layers (26, 27, 28) with different porosities and/or different lattice structures, through which layers the air channel system passes in succession.

16. Method according to claim 14, characterized in that the burner tip is produced in the powder bed (39) and the porosity of the layers with different porosities is formed by changing the introduction of energy into the powder bed (39) and/or by using different powders.

17. Burner with a burner lance (15), characterized in that a burner tip (19) according to one of claims 1 to 13 is provided at the end of the burner lance (15).